The complexity and cost associated with power dissipation in computing systems continues to grow with increasing demands on computing performance. These systems commonly employ numerous processors, application specific integrated circuits (ASICs) and memory devices, each of which must be designed or coupled with sufficient power dissipation capacity. Direct air cooling of devices may not be sufficient in systems incorporating highly dense physical architectures; instead, liquid cooling of such devices may be required in such instances.
In the prior art, certain techniques have been employed to directly couple fluid (e.g., water or alcohol) to the semiconductor package to address increased thermal dissipation. However, approximately two-thirds of the thermal resistance between the semiconductor junction and the ambient cooling fluid is internal to the semiconductor package. Accordingly, the internal thermal impedance dominates how thermal dissipation occurs, irrespective of coupling fluid or other thermal sinks. Accordingly, a reduction of the thermal impedance is needed in order to make significant improvement in thermal dissipation.
The prior art has also attempted to incorporate micro-channels with the semiconductor element (i.e., a “die”) to improve cooling efficiency. Each micro-channel is for example etched into the semiconductor substrate so as to provide increased area cooling to the substrate. By way of example, these micro-channels may form a series of “fins” in the substrate to assist in dissipating internally-generated heat. One difficulty with the prior art's use of micro-channels is that high pressure is used to couple heat transfer fluid to the die; that is, a pressure pump forces the fluid to flow through the micro-channels. This pressure pump has significant failure modes that make it risky to use within computing systems.
The prior art has also attempted to utilize “loop thermosyphon” techniques to cool the semiconductor package. Loop thermosyphon of the prior art utilizes an evaporator, such as a metal block, to thermally cool the semiconductor package with cooling liquid there between. The package heats up to generate vapor from the liquid; and the density differences between the liquid and the vapor create cooling between the evaporator and the semiconductor package. However, as discussed above, loop thermosyphon of the prior art does not solve the aforementioned reduction of the thermal impedance internal to the semiconductor package and, therefore, it does not dissipate the majority of the thermally generated energy internal to the package.
The invention provides techniques and methods for directly cooling the semiconductor die in order to reduce thermal impedances and to increase thermal dissipation, to facilitate increased performance and capacity for semiconductor devices. Other features of the invention will be apparent within the description that follows.